1. Field of the Invention
The invention relates to a flame starting unit for an internal combustion engine, especially a diesel engine with a flame glow plug which is located in an air intake channel of the internal combustion engine and which is supplied with fuel via a fuel line, and to a process for operating the flame starting unit.
2. Description of Related Art
A flame starting unit with a flame glow plug of the type to which the present invention is directed is known from German Patent Applications DE 4 243 959 A1 and DE 4 243 965 A1 and their corresponding U.S. Pat. Nos. 5,377,440 and 5,402,757, respectively. Such a flame starting unit is used to enable cold starting of an internal combustion engine.
In known flame starting units, the flame glow plug is supplied using fixed fuel metering which is designed for high thermal power in idle rpm of the internal combustion engine. This results in the fact that, in internal combustion engines with small piston displacement or internal combustion engines with low compression, problems can arise in the starting phase because the flame of the flame glow plug consumes too much oxygen, and therefore, a relative oxygen shortage occurs for the engine. As the result of this oxygen shortage, sufficient combustion in the internal combustion engine does not take place; this results in formation of white smoke due to unburned fuel and condensate formation. Furthermore, if the flame glow plug has a small nozzle or diaphragm design, the fuel supply of the flame glow plug is too low at higher rpm of the internal combustion engine.
In the known flame starting units, fuel is metered only via the size of the nozzle or aperture used in the flame glow plug and the fuel pressure. The amount of fuel cannot be controlled by the flame starting unit itself. However, the fuel pressures in the different systems of the various engine and vehicle manufacturers are so different over the entire rpm range that is metering of fuel for the flame glow plug is not enough to start the internal combustion engine at very low temperatures.